Fetal neuro-muscular activity is one of the basic physiological functions of the developing organism and is necessary for normal neural, muscular and skeletal development of the fetus. Fetoplacental unit dysfunction or severe impairment of nutrient supply by the maternal circulation are expected, and do, lead to decreased fetal neuro-muscular activity. Accordingly, it has long been recognized that there is a direct correlation between fetal movement and the health of the pregnancy, or in other words, the value of reduced fetal movement as a predictor of intrauterine fetal death.
This has led to the clinical use of fetal movement assessment in preventing fetal death and untoward pregnancy outcome, in both low and high risk pregnancies. For instance, in one study involving high risk pregnancies, women were asked to engage in fetal movement counting for at least one hour each day, and wherein a fetal movement count of three or less was considered abnormal. The predictive value for an unfavorable perinatal outcome with reduced fetal activity was similar to that of a nonreactive nonstress fetal heart test. The experience of fetal movement counting in high risk pregnancy has prompted the suggestion that fetal movement counting be applied as a means of fetal assessment to the general pregnant population. In certain studies, women counted fetal movements for one hour, two hours after a meal, three times weekly after 30 weeks gestation. Counts below three were repeated for a second hour, and women were instructed to report if the count remained at fewer than three per hour. When a reduction in fetal movement was perceived, further fetal evaluation, using ultrasound and antepartum heart rate monitoring, was instituted and delivery expedited if fetal movement remained reduced.
The results pointed toward a potential benefit of fetal movement counting in low risk pregnancy and with a low false-positive rate ranging from 1 to 8%. However, the rates of attrition reported for low risk patients assigned to a fetal movement counting protocol were higher than in high risk studies (30-50%). It is possible that patient motivation in a problem pregnancy may be higher as such patients are driven by concern about fetal condition, whereas low risk patients may regard any testing as "unnecessary intervention".
Maternal perception of fetal movement constitutes the most widely used method of fetal activity assessment in today's clinical practice.
The major drawback of this method of fetal activity assessment consists in the cumbersome tools presently used to record maternal perception of fetal activity. The cumbersome nature of maternal fetal movement counting process most probably represents the major reason for low patient compliance and low response to the alarm signals. Mothers can not be expected to record the time and intensity of all the fetal movements and usually record only the time at which the fetal movement counting started and the time when ten fetal movements were appreciated and the counting was thus discontinued. Recording the time of each perceived movement or the relative subjective strength of each movement is not possible without the assistance of a recording device which until now is not available. Comparison of the fetal movement patterns with previous records generated by the same mother and fetus pair is entirely impossible without the assistance of computer analysis. Assessment of patent's compliance with fetal movement counting or recording protocols can take place only at the time of prenatal visit. The day to day decision concerning adequacy of fetal activity is left to the patient who might doubt her ability to adequately assess the fetus and thus frequently ignores the warning and alarm criteria. Requiring the patient to interpret the record of fetal movement is not appropriate and has been amply demonstrated to be only partially effective.
Maternal compliance with any fetal movement counting protocol represents a major problem. Approximately only 80% of patients adhere to the counting protocol and only 40-60% of those counting report decreased fetal movements when required by the criteria set in their counting protocol. (2) Thus, fetal movement counting protocols are correctly exercised in only 50% of the patients participating in any fetal movement counting protocol. Thus, given the unreliability of the "measuring instrument", the mother, it is truly remarkable that great majority of the studies published to date clearly demonstrate clinical usefulness of fetal movement counting by the mother in preventing fetal death and compromise.
Maternally perceived fetal movement counting is undoubtedly beneficial. The difficulties encountered in implementing the different fetal movement counting protocols make the development of a device which would facilitate the recording of the maternally perceived fetal movement and standardize the interpretation of the movement record extremely important.
In spite of the apparent clinical importance of fetal movement in determining the well being of the pregnancy no instruments capable of recording maternally perceived fetal activity in non-invasive, unobtrusive, semi-quantitative, and partially objective fashion is presently commercially available.